[commit: ghc] master: Partially fix #367 by adding HpLim checks to entry with -fno-omit-yields. (d3128bf)

[Edward Z. Yang]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/d3128bfc286002862e916296629a22f1ce987e4e

>---------------------------------------------------------------

commit d3128bfc286002862e916296629a22f1ce987e4e
Author: Edward Z. Yang <ezyang at mit.edu>
Date:   Mon Sep 17 18:28:49 2012 +0200

    Partially fix #367 by adding HpLim checks to entry with -fno-omit-yields.
    
    The current fix is relatively dumb as far as where to add HpLim
    checks: it will always perform a check unless we know that we're
    returning from a closure or we are doing a non let-no-escape case
    analysis.  The performance impact on the nofib suite looks like this:
    
                Min          +5.7%     -0.0%     -6.5%     -6.4%    -50.0%
                Max          +6.3%     +5.8%     +5.0%     +5.5%     +0.8%
     Geometric Mean          +6.2%     +0.1%     +0.5%     +0.5%     -0.8%
    
    Overall, the executable bloat is the biggest problem, so we keep the old
    omit-yields optimization on by default. Remember that if you need an
    interruptibility guarantee, you need to recompile all of your libraries
    with -fno-omit-yields.
    
    A better fix would involve only inserting the yields necessary to break
    loops; this is left as future work.
    
    Signed-off-by: Edward Z. Yang <ezyang at mit.edu>

 compiler/codeGen/StgCmmExpr.hs |    4 +--
 compiler/codeGen/StgCmmHeap.hs |   57 ++++++++++++++++++++++++++--------------
 compiler/main/DynFlags.hs      |    4 +++
 docs/users_guide/using.xml     |   18 ++++++++++++
 4 files changed, 60 insertions(+), 23 deletions(-)


Diff suppressed because of size. To see it, use:

    git show d3128bfc286002862e916296629a22f1ce987e4e